Mastering Embedded Linux Programming - Second Edition

The anatomy of a device driver

It's time to draw some threads together by looking at the code for a simple device driver. Here is a device driver named dummy, which creates four devices that are accessed through dev/dummy0 to /dev/dummy3. The complete source code for the driver follows: you will find the code in MELP/chapter_09/dummy-driver:

#include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/device.h>#define DEVICE_NAME "dummy" #define MAJOR_NUM 42 #define NUM_DEVICES 4  static struct class *dummy_class; static int dummy_open(struct inode *inode, struct file *file) {   pr_info("%s\n", __func__);   return 0; }  static int dummy_release(struct inode *inode, struct file *file) {  ...